Cherimoya (Annona cherimola Mill) Polyphenoloxidase: Monophenolase and Dihydroxyphenolase Activities

Polyphenoloxidase (PPO) from cherimoya epicarp catalyzed the hydroxylation of monphenols like L(?)tyrosine, tyramine, and p-cresol (monophenolase activity), and oxidation of o-dihydroxyphenols like catechol and L-DOPA (dihydroxyphenolase activity). The hydroxylation of monophenols occurred after a lag period which was shortened by diphenols. The Km values indicated a low affinity of PPO to the substrates. Aliphatic mono- and dicarboxylic acids and sugars did not show any inhibitory effect on PPO cherimoya epicarp. Cysteine and mercaptoethanol, but not ascorbic acid, appeared to be protective agents of PPO cherimoya epicarp.     

Cubic CdS thin films studied by spectroscopic ellipsometry

CdS polycrystalline films were grown onto glass substrates by chemical bath deposition (CBD) and characterized by spectroellipsometry, X-ray diffraction and transmission electron microscopy. The X-ray diffraction patterns of the samples showed the presence of a CdS cubic phase (β-CdS) and of Cd2SiO4 as interfacial material. Using electron diffraction it was possible to index the films as cubic CdS. From effective dielectric function measurements and from reported optical data for the dielectric function of cubic CdS crystals, grown by vapour phase epitaxy, it was possible to fit the experimental data to an effective medium approximation, and to deduce the film thickness, the void fraction and the field screening. This revised version was published online in August 2006 with corrections to the Cover Date.     

SENSORY QUALITY OF CHICKEN MEAT AS A FUNCTION OF ITS FATNESS: COMPARISON OF MEAT LOAF WITH MEAT COOKED IN WATER1

Broiler chicken carcasses were classified as being lean, medium or fat, according to the proportion by weight of abdominal fat. The sensory quality was evaluated of breast and dark meat cooked separately in water, and of meat loaf containing both breast and dark meat. When cooked in water, the differences in the degree of fatness were found to have essentially no effect on the sensory quality. When cooked as meat loaf, the product of medium fatness was found to have the highest sensory quality, followed by the fat meat product and finally by the lean meat product.     

ANTIOXIDANT ACTIVITY COMPARISON OF THOMPSON GRAPE POMACE EXTRACT, ROSEMARY AND TOCOPHEROLS IN SOYBEAN OIL

The effect of natural antioxidants was tested by oxidative stability index (OSI) in refined soybean oil (RSO) using Rancimat method. Phenolic compounds of Thompson grape pomace were extracted with 95:5 (v : v) ethanol : water. The antioxidant activity of grape pomace extract (GPE) obtained was compared with those of rosemary extract (RE), and tocopherols mix (TM) known as covi-ox T-70. The synergistic effect of citric acid was also evaluated. Results showed a total phenols content of 17.39 mg ( + )-catechin equivalents per g of GPE. Thompson GPE at 0.3 and 0.5% (w/w) exhibited greater antioxidant activity than TM. RSO containing GPE or RE at 0.5% (w/w) showed an OSI higher than 48 h at 110C. Citric acid did not show synergistic effect with GPE. However, a synergistic effect for TM at 0.02% (w/w) with citric acid at 1.0% (w/w) was observed. Citric acid at 2.0% (w/w) with RE at all concentrations tested also displayed synergism.

PRACTICAL APPLICATIONS

Synthetic antioxidants are widely used in the food industry to delay fat oxidation; however, their utilization has been questioned due to toxicology concerns. Researchers have recognized the need to identify new natural antioxidants to use as additives. In this study, we measured total phenolics content of Thompson grape pomace extract (GPE) and found that the antioxidant activity of this extract was stronger than tocopherols from soybean oil. We propose that GPE can have applications as a food antioxidant.